This invention relates to lightwave optical component packages and, in particular, to an apparatus for aligning optical fibers and producing hermetic seals for such packages.
Lightwave transmitters typically take the form of a light source, such as a laser or light-emitting diode, mounted on a stud within a housing, with an optical fiber aligned with the source and extending through the housing wall. Similarly, a lightwave receiver will have a photodetector such as a pin diode in alignment with a fiber extending through a housing. A transceiver could include both light source and detector within a single housing, and a light switch could include fibers positioned through two or more housing walls and aligned with other fibers within the package.
In all such types of lightwave component packages, it is often desirable and even necessary to hermetically seal the component within the housing to prevent deterioration due to atmospheric conditions. This is especially true for terrestrial or submarine systems where the components must last for several years and cannot be repaired easily. The fact that one or more fibers must extend through the package housing and that these fibers must be precisely aligned with the component within the housing makes hermetic sealing quite problematic, especially in the case of single mode fibers, which have a very small core (typically, diameters of approximately 8 .mu.m).
Proposals have been made regarding achieving hermetic seals in optical component packages. For example, U.S. Pat. No. 4,119,363, issued to Camlibel et al, suggests threading the fiber through a metal tube, filling the tube with solder, and then allowing it to cool so that the solder forms an hermetic seal. The tube-fiber assembly is then inserted through an aperture in the housing which is covered by a ferrule with a flange exterior to the housing. The fiber is aligned with the component and then the tube is soldered to the outside flange.
While such proposals are generally adequate for multimode fibers, the use of a soldering operation to lock the tube into place is difficult to implement since the use of flux could damage the component, and solder may not always wet the appropriate areas of the package. Further, the fiber has to be aligned with the component prior to soldering by a difficult and time-consuming operation involving a multiplicity of micropositioners. In addition, where single mode fibers are being aligned, the expansion and later contraction of the elements due to the heat of the soldering operation usually results in misalignment.
It is, therefore, a primary object of the invention to provide an optical component package with an hermetic seal. It is a further object of the invention to provide an assembly which produces such a seal and allows a quick but stable alignment of the fiber with the component within the housing. It is a still further object of the invention to provide an assembly which permits alignment of single mode fibers.